Alternating-current motor.



No. 630,489. Patented Aug. 8, I899. nm.

ALTERNA CURRENT MOTOR.

(Lppliclflon filed Im. 19, 1898.)

WITNESSES: INVENTOR J00 wM' z/ M nm 4 H\ SATTORNEYS.

UNITED STATES PATENT OFFICE.

MAX DERI, OF VIENNA, AUSTRIA-HUNGARY.

ALTERNATlNG-CURRENT MOTOR.

SPECIFICATION forming part Of Letters Patent No. 630,489, dated August8, 1899. Application filed January 12, 189 8. $erial No. 666,415. (NomodeLl To all whom it may concern:

Be it known that I, MAX DERI, a subject of the Emperor ofAustria-Hungary, residing at Vienna, in the Province of Lower Austria,in the Empire of Austria-Hungary, have invented certain new and usefulImprovements in Alternate-Current Motors; and I do hereby declare thefollowing to be a full, clear, and exact description of the invention,such as will enable others skilled in the art to which it appertains tomake and use the same, reference being had to the accompanying drawings,and to letters and figures of reference marked thereon, which form apart of this specification.

It is generally useful to place starting-resistances into the circuit ofthe induced windings of electromotors for monophase or polyphasealternating current. By this means the starting-torque will beincreased. The general practice for this purpose is to providecollector-rin gs on the armature and by means of brushes to insert theresistances in the armature-coils. The resistances are to be cut out ofcircuit as soon as the motor has reached a certain speed. This methodimplies several complications in the construction of the armature anddiminishes its efficacy. Another way of accomplishing a similar object,especially with monophase-motors, is the use of a commutator inconnection with the armature-coils in order to obtain by shifting andinterconnecting the brushes a considerable start-ing-torque. The inducedcurrents need to pass through commutator and brushes only during thestarting period, and the motor after having reached a certain speed willwork only by the induction of the closed armature-windings, so thatcommutator and brushes then are of no use. By the following new devicesthe resistances and commutators are so arranged in a very simple way inconnection with the armature that they may be put into or out of actionwithout special external leads being connected to the armature-wires andwithout special switchinggears being actuated in the armature-circuits.

Figure 1 represents a set of windings, and Fig. 2 a set of coils, whichare placed on the armature and connected in such a way that in afour-pole alternating field, Figs. 1 and 2, they carry the inducedcurrents in series forming a closed circuit. In a two-pole field, Figs.1 and 2, however, they are Without current, the sum of electromotiveforces induced in all the windings or coils of the set being zero inevery position. In a four-pole field the current flows in the order 1 1,2, 2 3 3, 4, 4 1, and no difference of potential will occur between theconnecting points aand a nor a and a. In a twopole field, however, adifference of potential will appear between these points. Thereforeleads connecting the points a and a or a and a will be without currentin a four-pole field and currents will pass through them in a two-polefield. By providing such four-pole closed windings or coils on thearmature and by connecting the points a a by means of suitableresistances 0" r, the latter forming coherent parts of the armature-windings, the object is obtained that in a two-pole field theresistances will help to increase the starting-torque; but after asuitable speed is reached the field will be changed to a four-pole oneand the resistances thereby get out of action. Fig. 3 shows a diagram ofconnections between the armature-windings of a monophase-motor and acommutator according to this method, the object being to produce byshifting and connecting the brushes a considerable starting moment. Inthis case the connect-ingpoints of the windings or coils are not to bedirectly joined as above in order to form individual closed circuits,but similar to the winding of a drum-armature in an ordinary dynamo thepoints 11 b c n a are connected together with the commutator-bars. It isuseful even in this arrangement to give a suitable resistance to theconnections between the points a Z; c n and the com mutatorbars. By thismeans, besides obtaining the principal object of increasingthestartingtorque, we will also avoid the sparking of the brushes. If suchan armature is exposed to a two-pole alternating field, differences ofpotential will take place between the points a a 12 b Induced currentspass through the connecting-wires a b b c n a and through the brushesand generate a starting-torque. After the proper speed is reached thefield will be changed into afour-pole one. The induced currents flow inthe closed windings and coils and cause the armature to be keptrotating. Then no difference of potential exists between the points a aZ) I)", and therefore no current passes through the connecting-wires aZ) Z) c n (t' to the commutator and the brushes. The armature-Wires canbe used to better advantage in a two-pole field if resistances orcommutators are inserted at both front faces of the armature inconnection with all the proper points of the windings. In order to makethe motor-field in all these cases now two-pole and then four-pole, thefield-coils are to be arranged in COlllblIlfL tion with a switch U, asrepresented in Fig. &. The arrows in this diagram are to indicate thedirection of the magnetic flux. By respective position of theswitching-gear either Ct is connected with (Z and b with 0, whereby atwo-pole field is produced, or a is connected with c and Z) with (1,resulting in a four-pole field. This diagram refers to a monophasemotor;but it is easily seen that the arrangement by multiple switches may beapplied in an analogous way to polyphase fields. The switching is doneby hand or automatically.

In the example described and shown there are two poles and four poles;but it is obvious that other numbers of poles can be used. In case aneven number of poles be chosen for one mode of working, an even, but adilterent, number is chosen for the other mode of working. It ispreferable in each case to have one number a multiple of the other. Itis also preferable to use the smaller number of poles for starting themotor and the larger number for the normal working.

I claim as my invention- 1. In alternate-current motors, the combinationof sets of windings or coils in the ar mature with resistanceconnections which are inserted between the junctions of the windings orcoils in such a manner that in an alternating field witha certainnumberof poles the induced currents pass through the said connectionsbut in an alternating iield, the

number of poles of which is diiterent from above, these connections haveno current, and switching devices arranged in connection with thefield-coils for producing in the motor fields having a dilterent numberof poles with different positions of the switching devices,substantially as described.

2. In monophase alternate-currentmotors, the combination of sets ofwindings or coils on the armature with a commutator, the bars of whichare connected with the junctionpoints of the windings or coils in such amanner that in an alternating field with a certain number of poles theinduced current-s pass through the commutator and brushes, generating astarting-torque, but in an alternating field the numberof poles ofwhichisdiilerent from the above, the commutator and the brushes arewithout current and switching devices arranged in connection with theiieldcoils for producing in the motor fields having a different numberof poles with diticrent positions of the switching devices,substantially as described.

3. The mode herein described of operating an alternate-current motorhaving armatureeoils with resistances connected between cortain pointsof the same, consisting in prod ucing in the field-magnets a givennumber of poles and passing the induced currents through the armaturecoils and resistances, and thereby increasing the starting-torque, andthen for the normal working producing in the same field-magnetsadiit'erentnumber of poles, and preventing thereby any difference ofpotential from arising in the said resistance connections of thearmature-coils, substantially as described.

In testimony whereof I allix my signature in presence of two witnesses.

MAX DIG H. lVitncsscs:

HENRY C. CARPENTER, Onas. E. CARPEN'IER.

